Synthesis and evaluation of novel series of Schiff base cationic surfactants as corrosion inhibitors for carbon steel in acidic/chloride media: experimental and theoretical investigations

Abstract

A new family of Schiff base cationic surfactants (CSSB) having various alkyl chain lengths were prepared and their chemical structure was elucidated by using different spectroscopic techniques (FTIR, ¹³C-NMR and ¹H-NMR). The surface activity parameters of the prepared surfactants were measured to set the adsorption and micellization characteristics at the water/air interface. The corrosion inhibition capability of these surfactants was investigated on a carbon steel surface in 3.5% NaCl⁺ 0.5 M HCl solutions at different temperatures (30–60 °C) by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The results revealed that CSSB compounds inhibited corrosion of carbon steel in the investigated acidic chloride containing environment. It was found that the inhibition efficiency increases with an increase in inhibitor concentrations and decreases with increasing temperature. Polarization data indicated that the investigated compounds act as mixed-type inhibitors, and the adsorption isotherm basically obeys the Langmuir isotherm. The corrosion inhibition mechanism was discussed based on the potential of zero charge value. An SEM/EDX studies confirmed that CSSB inhibitors could form films by adsorption on the carbon steel surface. The theoretical predictions exhibit good agreement with empirical results.